The pneumatic fender is arranged to hermetically seal the air inside to obtain a predetermined characteristics such as mitigation of the impact. Therefore, it is preferable to know the internal pressure for having the normal function. In recent years, provided have been various methods for knowing the internal pressure of the pneumatic fender by receiving the sensed signal from the air pressure sensor installed inside the pneumatic fender by the radio communication (for example, see Japanese Patent Application Laid-Open No. 8-43226 and Japanese Patent Application Laid-open No. 2007-178214).
Conventionally, the air pressure sensor is fixedly installed in a stable state in the bag or to a cap member, and therefore the installation operation or the replacement operation of the air pressure sensor requires the removal of the cap member after the landing of the fender and the discharging of the air in it. Thus, there has been a problem that it requires significant time and labor in the operation for installing the air pressure sensor inside the fender bag and the operation for replacing it.